I like to mix atonal sections with more conventional sections, alternating, used to compliment each other. A sweet piece of music sounds even sweeter after something strange. A strange piece of music sounds even cooler after something familiar, etc. I like range.
Here's some stuff I did for Brainpipe, a short medley. Some of it gets atonal, but I'll come back to more conventional harmony from time to time.
http://nightmareband.bandcamp.com/track/brainpipe-ii-trippocampus[edit: sorry -wrong url!]
This is a collection of some of the medium intensity pieces used in the game. There's also a set of mellow intensity loops and a set of maximum intensity pieces, each to match increasingly difficult sections of the game.